Add @static* annotations where they are missing.

Initialize all static vars that are not, most to `null`.

See #32444.


git-svn-id: https://develop.svn.wordpress.org/trunk@32650 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/compat.php

@@ -20,6 +20,8 @@ if ( !function_exists('_') ) {
  * @since 4.2.2
  * @access private
  *
+ * @staticvar string $utf8_pcre
+ *
  * @param bool $set - Used for testing only
  *             null   : default - get PCRE/u capability
  *             false  : Used for testing - return false for future calls to this function